"I know how hard it is," Garth tells PEOPLE when it comes to divorce. "I've said many times to myself, 'I can't imagine that happening to me.' It was the unimaginable to me. But guess what, it happened and I got through it."

"As I turn 40, I want to share my life with other women," says Garth. "I've gradually been making my way to this point in my life. I want to share my voice."

The actress, best known for her starring role on Beverly Hills, 90210, says: "You can feel really bad about yourself when you're going through a divorce. You can feel like a failure. And that's not a good feeling. [By sharing my story] maybe it'll help someone. I've gone through this and so can you."

'The Best for Both of Us'

Garth also wants to make it clear she's not a victim.

"At first, I wanted to say that [our marriage] is not working for him and he's the one that's not happy," she says. "But when I really looked into how I was feeling, I could see it was the best thing for both of us. I didn't want to admit it, because I didn't want to let him go."

She also wants to stay positive for the couple's three daughters, Luca, 14, Lola, 9, and Fiona, 5½, who will star with Garth on her new reality show, Jennie Garth: A Little Bit Country, premiering on CMT April 20.

"I hope I don't come off as pathetic and sad, because I'm not," Garth adds. "I want to be a symbol of getting through something like this intact. I've gone through the darkest parts and I'm coming out and I even feel gratitude for having gone through it."